add new constructor to redisscheduler

webmagic-extension/src/main/java/us/codecraft/webmagic/scheduler/RedisScheduler.java

@@ -29,6 +29,10 @@ public class RedisScheduler implements Scheduler {
         pool = new JedisPool(new JedisPoolConfig(), host);
     }
 
+    public RedisScheduler(JedisPool pool) {
+        this.pool = pool;
+    }
+
     @Override
     public synchronized void push(Request request, Task task) {
         Jedis jedis = pool.getResource();